1. Field of the Invention
This invention relates to a self-timer device for a motion picture camera and, more particularly, to a self-timer device which is driven by an electric motor provided for driving certain moving parts of the camera and which controls the timing for starting and stopping the release of the camera, i.e. the time intervals between setting for an automatic photographing and the actual start of it and between the start of photographing and the end of it, to enable an automatic photographing operation while being driven by the electric motor.
2. Description of the Prior Art
For automatic photographing of a scene with a motion picture camera, a self-timer device for automatically stopping a release arrangement of the camera a preset period of time after the start of the camera release is known as disclosed, for example, by a Japanese patent publication No. Sho 42-16578.
In the device disclosed by the patent publication No. Sho 42-16578, there are provided a restricting member which restricts a shutter release member in its operating position when it is operated and a restriction removing member which works on the restricting member to remove the above stated restriction. When the release member is operated to start a photographing operation, the release member is restricted in its operative position and, at the same time, the restriction removing member is shifted in response to a driving device of the camera in such a manner that the restriction on the shutter release member by the restricting member is removed to return the shutter release member to its inoperative position when a predetermined length of time has elasped so that the photographing operation can be automatically terminated.
One of the main purposes of a self-timer device for a motion picture camera is, as it is so with self-timers of still picture cameras, provide for the participation of the photographer himself in the scene being photographed. Using the self-timer device disclosed in the patent publication cited above, the photographer is allowed to participate only from the midst of the scene after he has operated the shutter release member. Such participation, then, tends to make the scene very unnatural.
To eliminate such inconvenience, there have been proposed and have been actually marketed other self-timers that permit controlling the time interval between setting for automatic photographing and the actual start of it (will be called "waiting time" hereinafter) as well as another time interval between the start of photographing and the end of it (hereinafter will be called "photographing time").
In an example of such conventional self-timer devices, there is provided an electric timer circuit which can control both the waiting time and the photographing time; the output of the timer circuit is used to control the on-off timing of switching means which is connected to an electromagnetic release arrangement of the camera in such a way as to start photographing by actuating the release arrangement after the waiting time has elapsed and to stop the operation of the release arrangement when the photographing time has elapsed. There is also another example wherein a pure mechanical control arrangement is employed instead of such an electrical control arrangement. In the mechanical arrangement, a controlling member is driven by a spring member through a governor mechanism to control the timimg for starting and terminating the camera release for automatic photographing.
However, the former example of the prior art requires the use of a plurality of time constant arrangements for controlling different time intervals. This makes the circuit arrangement more complicated. On the other hand, in the latter example, the driving force obtainable from the spring member alone is not sufficient and the insufficient driving force tends to cause variation in the time intervals to be controlled thereby.
In view of these drawbacks of the conventional devices, the assignee of the present invention has previously proposed in U.S. Pat. Application Ser. No. 595,008, filed July 11, 1975, a self-timer device which uses an electric timer circuit to control only the waiting time while the photographing time is controlled by utilizing the rotational frequency or rotating degree of a motor which drives a film feeding device and a shutter device of the camera.
However, even the device of Ser. No. 595,008 necessitates the use of an electric timer circuit for the purpose of controlling the waiting time. Generally a circuit of this type comprises electric elements such as capacitor, resistor, etc. and is vulnerable to a leakage current, variation in the ambient temperature, etc. The circuit therefore tends to cause variation in the controlled time intervals in automatic photographing operations.